RF transmission of video signals is commonly performed for certain applications. For example, television stations routinely broadcast such video signals on a variety of frequency bands, which may then be received and displayed by television sets. Furthermore, unmanned surveillance aircraft used for crowd observation also broadcast video signals on a variety of frequency bands. Tuning a receiver to a known frequency to receive a video signal transmitted on that frequency is quick and simple. However, when no specific frequency is known, and instead merely a band of frequencies, tuning a receiver to find a video signal being transmitted at a given frequency within the band of frequencies can be time consuming, as each frequency within the band may be checked.
To add to this difficulty of finding a given frequency on which the video signal is being transmitted, the video signal may be an analog or a digital video signal. Therefore, when both the form (analog or digital) of the video signal and the given frequency on which it is being transmitted are unknown, a separate analog and a separate digital receiver are typically used to find the video signal. Each receiver is made to scan each frequency of the band. As such, detection of a video signal with an unknown form and being transmitted on an unknown frequency can be time consuming for even advanced hardware.
Attempts at making receivers to speed up this process have been made. For example, U.S. Pat. Pub. 2009/0122205 to Xing et al. discloses a television receiver including separate analog and digital video tuners. Each tuner is configured to separately scan a plurality of channels for a video signal. An analog decoder determines whether the analog video tuner has found a video signal on a given channel, while a digital decoder determines whether the digital video tuner has found a video signal on the given channel. The television receiver of Xing et al., however, suffers from some drawbacks. For example, both the analog and the digital tuner check each channel for the presence of a video signal, even though one of the tuners may have determined that there is no signal on a given channel.
U.S. Pat. No. 7,322,039 to Tsubouchi et al. discloses a broadcasting receiver for receiving analog and digital video signals. The broadcasting receiver includes an analog tuner and a digital tuner. The analog tuner and the digital tuner are configured to concurrently scan a plurality of channels for video signals. A main CPU determines whether the digital tuner has found a digital video signal, while a sub-CPU determines whether the analog tuner has found an analog video signal. Tsubouchi et al. suffers from similar drawbacks to Xing et al., however. Both the analog and the digital tuner check each channel for the presence of a video signal, even though one of the tuners may have determined that there is no signal on a given channel.
Given the drawbacks of the prior art, further advances in communications devices able to scan a range of frequencies for analog and digital video signals may be desirable.